The primary long term objective is to develop instrumentation and test methodology that will offer researchers and clinicians markedly improved information from the caloric test of the vestibular system. Subordinate objectives are to allow the test to be administered more easily, with less patient discomfort and in a more cost effective manner. The first step, Phase I, will be the specification design and demonstration of the prototype of an instrument making these improvements possible. The instrument envisioned will provide a more accurate and repeatable thermal stimulus to the inner ear than presently available devices. More importantly, the novel aspect of this instrument will be its ability to deliver programmed control of irrigant temperature such as stepped, ramped or other patterned changes. This will improve the quantitation of results, reduce amount of stimulus the patient will be required to accept and possibly make the changes less uncomfortable for the subjects by making changes less abruptly. Specific aims for this phase are to 1) finalize the approach (concept), 2) design and construct a prototype 3) bench-test the prototype 4) perform a clinical evaluation of the prototype 5) publish the results and prepare specifications for a commercial version of the instrument, Phase II. These aims will be accomplished through the combined efforts of ICS Medical Corporation and the resources of the vestibular testing laboratory of The Johns Hopkins Hospital. By providing this instrument at approximately the same price as commercial systems presently available, it is anticipated that researchers will develop improved test procedures. Also clinicians will be able to immediately upgrade their test capabilities. Finally, some physicians, especially those in Europe who have expressed dissatisfaction with caloric testing due to its lack of precision can be expected to rethink their attitude toward this unique test.